Electronic packages of the variety described above are known in the art, with examples defined in detail in U.S. Pat. Nos. 4,849,856 (Funari et al), 4,914,551 (Anschel et al), 5,003,429 (Baker et al) and 5,009,393 (Bentlage et al), all of which are assigned to the same assignee as the present invention. As defined therein, these packages may include a chip electrically coupled to one side of a flexible circuit member which is typically of a dielectric, e.g., polyimide, having at least one layer of circuitry, e.g., copper, thereon. Such a chip may be coupled, electrically, to the flexible circuit member's circuitry using solder, one well known technique currently used by the assignee of the present invention and referred to as a controlled collapse chip connection (a/k/a C4) procedure. The flexible circuit (a/k/a tape) may then be coupled electrically to respective circuitry, e.g., copper pads or lines, formed on the top surface of a printed circuit board or the like. Such boards, usually comprised of several layers of dielectric material, e.g., fiberglass-reinforced epoxy resin, interspersed with various conductor levels, e.g., power, signal and/or ground planes, are known in the art and further definition is not believed necessary. Finally, such packages typically utilize a heat sink member which is thermally coupled to the chip to enhance heat removal from the completed package during operation. Such a heat sink usually comprises a metallic, e.g., aluminum, element located atop the board with appropriate "feet" firmly oriented on the board's upper surface externally of the aforementioned flexible circuit. The heat-generating chip may be thermally coupled to the heat sink using an appropriate thermal adhesive, several of which are known in the art. To further promote heat removal, the heat sink typically includes appropriate fins or the like at designated locations thereon.
It is known in package assemblies of the type defined above to electrically couple the outer leads of the flexible circuit to the respective conductors on the circuit board using solder. In one known technique for soldering such leads, the dielectric material of the flexible circuit member is removed (etched away) along the flexible circuit's periphery to expose the terminal ends of the outer lead conductors. Solder is applied to the board's conductors and the outer leads are aligned therewith and positioned on the solder. Heat is then applied, e.g., using a thermode structure, to effect the solder bond between respective pairs of conductors (flexible circuit and board). Such a form of connection requires that each of the relatively small terminal ends of the outer leads be substantially entirely free of dielectric, which has proven to be an expensive and time-consuming process, typically involving etching of the dielectric material using known etchants. Use of acids and caustics at elevated temperatures during such processing may also prove undesirable from an environmental standpoint.
The electronic package and method of making same in accordance with the teachings of the instant invention eliminate the need for such dielectric removal (and thus the need for an etching or the like process at this stage), while still assuring precise orientation and electrical coupling (e.g., soldering) of the flexible circuit's outer lead conductors to respective conductors on the package's circuit board structure. The invention is capable of being readily implemented at reduced cost, and is also adaptable to mass production techniques for packaging structures.
It is believe that such an electronic package assembly and method of making same would constitute a significant advancement in the art.